Analysis of Mono-, Di- and Oligosaccharides by CE Using a Two-Stage Derivatization Method and LIF Detection.

A sensitive CE with LIF method has been developed for quantitative analysis of small carbohydrates. In this work, 17 carbohydrates including mono-, di- and oligosaccharides were simultaneously derivatized with 4-fluoro 7-nitrobenzo furazane (NBD-F) via a twostep reaction involving reductive amination with ammonia followed by condensation with NBD-F. Under the optimized derivatization conditions all carbo-hydrates were successfully derivatized within 2.5 h and separated within 15 min using borate buffer (90 mmol/L, pH 9.2). For sugar standards LODs were in the range of 49.7 to 243.6 nmol/L. Migration time and peak area reproducibility were better than RSD 0.1 and 3%, respectively. The method was applied to measure sugars in nanoliter volume samples of phloem sap obtained by stylectomy from wheat and to honeydew samples obtained from aphids feeding from wheat and willow

Can Tropical Insects Stand the Heat? A Case Study with the Brown Planthopper Nilaparvata lugens (Stål)

The brown planthopper Nilaparvata lugens (Stål) is the most serious pest of rice across the world, especially in tropical climates. N. lugens nymphs and adults were exposed to high temperatures to determine their critical thermal maximum (CTmax), heat coma temperature (HCT) and upper lethal temperature (ULT). Thermal tolerance values differed between developmental stages: nymphs were consistently less heat tolerant than adults. The mean (± SE) CTmax of nymphs and adult females and males were 34.9±0.3, 37.0±0.2 and 37.4±0.2°C respectively, and for the HCT were 37.7±0.3, 43.5±0.4 and 42.0±0.4°C. The ULT50 values (± SE) for nymphs and adults were 41.8±0.1 and 42.5±0.1°C respectively. The results indicate that nymphs of N. lugens are currently living at temperatures close to their upper thermal limits. Climate warming in tropical regions and occasional extreme high temperature events are likely to become important limiting factors affecting the survival and distribution of N. lugens

Are chlorophyll concentrations and nitrogen across the vertical canopy profile affected by elevated CO2 in mature Quercus trees?

Key message: In mature Q. robur, chlorophyll varied with season and canopy height, whilst eCO2-driven changes were consistent with Marea, highlighting key factors for consideration when scaling photosynthetic processes and canopy N-use. Nitrogen-rich chlorophyll and carotenoid pigments are important in photosynthetic functioning. Photosynthetic pigments have been found to decrease with elevated CO2 (eCO2), but few such studies have been done in aged forest trees. This study aimed to assess the effects of eCO2 (150 μmol mol−1 above ambient) and canopy position on chlorophyll content in mature Quercus robur (Q. robur). Over 5000 in situ chlorophyll absorbance measurements, alongside laboratory chlorophyll extractions, were collected on canopy-dominant Q. robur in the 3rd and 4th season of CO2 fumigation of a free-air CO2 enrichment (FACE) study in central England. Mass-based chlorophyll concentration (Chlmass, mg g−1) was significantly higher in the lower canopy compared to upper canopy foliage (P < 0.05). In contrast, significantly higher chlorophyll content (Chlarea, mg m−2) was observed in the upper canopy. ECO2 did not affect Chlmass but Chlarea significantly increased, attributable to increased leaf mass per unit area (Marea, g m−2). We found no effect of eCO2 on mass-based or area-based nitrogen (Nmass, mg g−1 or Narea g m−2); however, Narea significantly increased with canopy height, again attributable to Marea. The parallel relationships between Marea, Narea and Chlarea suggest the allocation of N to light harvesting is maintained with eCO2 exposure as well as in the upper canopy, and that increased photosynthetic mass may help regulate the eCO2 variation. An understanding of changes in the light-harvesting machinery with eCO2 will be useful to assess canopy processes and, at larger scales, changes in biogeochemical cycles in future climate scenarios

A mutation in amino acid permease AAP6 reduces the amino acid content of the Arabidopsis sieve elements but leaves aphid herbivores unaffected

The aim of this study was to investigate the role of the amino acid permease gene AAP6 in regulating phloem amino acid composition and then to determine the effects of this altered diet on aphid performance. A genotype of Arabidopsis thaliana (L.) was produced in which the function of the amino acid permease gene AAP6 (At5g49630) was abolished. Plants homozygous for the insertionally inactivated AAP6 gene had a significantly larger mean rosette width than the wild type and a greater number of cauline leaves. Seeds from the aap6 mutant were also significantly larger than those from the wild-type plants. Sieve element (SE) sap was collected by aphid stylectomy and the amino acids derivatized, separated, and quantified using Capillary Electrophoresis with Laser Induced Fluorescence (CE-LIF). In spite of the large variation across samples, the total amino acid concentration of SE sap of the aap6 mutant plants was significantly lower than that of the wild-type plants. The concentrations of lysine, phenylalanine, leucine, and aspartic acid were all significantly lower in concentration in the aap6 mutant plants compared with wild-type plants. This is the first direct demonstration of a physiological role for an amino acid transporter in regulating SE composition in vivo. The amino acid availability in sieve element sap is thought to be the major limiting factor for aphid growth and reproduction. Despite the changes in their diet, the aphid Myzus persicae (Sulzer) displayed only small changes in feeding behaviour on mutant plants when measured using the Electronic Penetration Graph (EPG) technique. Salivation by the aphid into the SE (E1 phase) was increased on mutant plants but there was no significant effect on other feeding EPG behaviours, or in the rate of honeydew production. Consistent with the small effect on aphid feeding behaviour, there was only a small effect of reduced sieve element amino acid concentration on aphid reproduction. The data are discussed in relation to the regulation of phloem composition and the role of phloem amino acids in regulating aphid performance

Reduced signal for polygenic adaptation of height in UK Biobank

Several recent papers have reported strong signals of selection on European polygenic height scores. These analyses used height effect estimates from the GIANT consortium and replication studies. Here, we describe a new analysis based on the the UK Biobank (UKB), a large, independent dataset. We find that the signals of selection using UKB effect estimates are strongly attenuated or absent. We also provide evidence that previous analyses were confounded by population stratification. Therefore, the conclusion of strong polygenic adaptation now lacks support. Moreover, these discrepancies highlight (1) that methods for correcting for population stratification in GWAS may not always be sufficient for polygenic trait analyses, and (2) that claims of differences in polygenic scores between populations should be treated with caution until these issues are better understood.Editorial noteThis article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter)

Ct threshold values, a proxy for viral load in community SARS-CoV-2 cases, demonstrate wide variation across populations and over time.

BACKGROUND: Information on SARS-CoV-2 in representative community surveillance is limited, particularly cycle threshold (Ct) values (a proxy for viral load). METHODS: We included all positive nose and throat swabs 26 April 2020 to 13 March 2021 from the UK's national COVID-19 Infection Survey, tested by RT-PCR for the N, S, and ORF1ab genes. We investigated predictors of median Ct value using quantile regression. RESULTS: Of 3,312,159 nose and throat swabs, 27,902 (0.83%) were RT-PCR-positive, 10,317 (37%), 11,012 (40%), and 6550 (23%) for 3, 2, or 1 of the N, S, and ORF1ab genes, respectively, with median Ct = 29.2 (~215 copies/ml; IQR Ct = 21.9-32.8, 14-56,400 copies/ml). Independent predictors of lower Cts (i.e. higher viral load) included self-reported symptoms and more genes detected, with at most small effects of sex, ethnicity, and age. Single-gene positives almost invariably had Ct > 30, but Cts varied widely in triple-gene positives, including without symptoms. Population-level Cts changed over time, with declining Ct preceding increasing SARS-CoV-2 positivity. Of 6189 participants with IgG S-antibody tests post-first RT-PCR-positive, 4808 (78%) were ever antibody-positive; Cts were significantly higher in those remaining antibody negative. CONCLUSIONS: Marked variation in community SARS-CoV-2 Ct values suggests that they could be a useful epidemiological early-warning indicator. FUNDING: Department of Health and Social Care, National Institutes of Health Research, Huo Family Foundation, Medical Research Council UK; Wellcome Trust